The controlled delivery of a preselected quantity of a beneficial agent to a patient is highly desirable in a number of situations. Particularly, the controlled delivery of drugs such as analgesics is highly desirable as there is great difficulty in properly administering analgesics. The need to administer analgesics varies greatly from patient to patient. Such factors as, for example, age, pain tolerance, renal function, and presence of other medications can all affect the pharmacokinetics of such analgesic.
In the area of analgesic administration, there has been much activity in the last several years directed towards letting the patient control how much drug he or she administers. It has been found that, as a group, patients controlling the quantity they receive use less analgesic than patients who must request the administration of a pain killer. One apparent factor is the psychological relief present when a patient knows he or she is in control of the amount of drug to be administered. The amount of drug the patient can self-administer must also be subject to a maximum level of drug.
The efficient patient controlled administration of drug has resulted in several devices on the market. Such devices generally suffer from several drawbacks. Initially, such devices are electromechanical in nature thus requiring an electrical power source. In addition, such devices are large and bulky which limits the patient's freedom to move.
Another drawback of such devices is that they only provide an on-demand rush of the drug as administered by the patient with no constant drug flow to the patient. While this type of drug administration is appropriate for many situations, it is often desirable to have a constant flow of drug to the patient, referred to herein as a continuous flow, supplemented by a patient controlled supplement of drug, referred to herein as a bolus flow. While several devices on the market are designed to provide such continuous flow supplemented by a patient controlled flow, such devices are again electro-mechanical in nature and are large and bulky thus limiting the patients' ability to move.
While, of course, two separate devices can be utilized to provide this continuous-bolus flow arrangement, such use of two devices adds to the cost and complexity of the system while further limiting patient mobility. What is thus needed is an apparatus and system for both a constant delivery of a beneficial agent and a patient controlled supplement of the beneficial agent which is low in cost, highly mobile, and easy to use. The present device meets these requirements.